1. Field of the Invention
The present invention relates to a circulating-type hot-water supply device including a function of maintaining a hot water inside a hot water supply pathway to a suitable temperature, by circulating the hot water inside the hot water supply pathway via a heat exchanger during stopping supply of hot water.
2. Description of the Related Art
Conventionally, in a hot-water supply device which heats water supplied to a water supply path by a heat exchanger heated by a burner, and which supplies hot water to a hot water supply path, a circulating-type hot-water supply device equipped with a communicating path which communicates a vicinity of a downstream end of the hot water supply path and the water supply path, and a circulating pump which circulates water inside a circulating circuit formed from the water supply path, the hot water supply path, and the communicating path via a heat exchanger (for example, refer to Japanese Patent Application Laid-Open No. 2007-263403).
In the circulating-type hot-water supply device mentioned above, the circulating pump is actuated full-time. Further, by heating the water running through the heat exchanger by arbitrarily combusting the burner even during stopping of the supply of hot water, the hot water inside the circulating circuit is maintained to a suitable temperature, and the hot water of the suitable temperature is immediately ejected when a hot water faucet is opened.
In a region with a high hardness of tap water, precipitates (scale) tends to adhere to an inner surface of an endothermic tube in the endothermic tube of the heat exchanger, from CaCo3 or MgCo3 contained in water. When the precipitates adhere as is explained above, a temperature of the heat exchanger rises from degradation of a heat exchange efficiency of the heat exchanger, and deterioration of the heat exchanger may occur originating from the temperature rise.
Therefore, in the circulating-type hot-water supply device mentioned above, when the hot water faucet is closed and the burner is combusting, a flow control valve is closed and the circulation of the hot water inside the circulating circuit is stopped (the burner is extinguished by this stopping), and determines that the heat exchanger is in an abnormal state from adhesion of the precipitates, when a temperature rise range of the hot water in the vicinity of an outlet of the heat exchanger from the time the valve is closed becomes equal to or higher than a predetermined threshold value.
In the circulating-type hot-water supply device mentioned above, the circulating pump is actuated full-time. Therefore, even when the circulation of the hot water inside the circulating circuit is stopped by the flow control valve, the circulating pump is continuing its operation. In this case, there is an inconvenience that the circulating pump runs idle, so that a load of the circulating pump becomes excessive and the circulating pump overheats, so that the circulating pump deteriorates.
The present invention has been made in view of such background, and aims at providing a circulating-type hot-water supply device capable of preventing overheat of a circulating pump, and which could determine that the heat exchanger is in an abnormal state from adhesion of precipitates.